使用Stack构建Yesod-SQLite测试项目时遭遇Aeson错误求助

Hey there, fellow Yesod/Stack newcomer! It’s super frustrating when a bug that’s supposed to be fixed still pops up—let’s work through this Aeson error together.

Even though the issue was marked fixed in Aeson 1.6.1, here are some common reasons you might still hit it with 1.6.3, plus fixes to try:

• Double-check your project’s resolver
  Stack’s resolver dictates which package versions your project uses, even if you have a newer Stack CLI version. Run stack resolver in your project folder to see which resolver you’re on. If it’s an older snapshot that predates the Aeson fix, update the resolver field in your stack.yaml to a newer version that includes Aeson 1.6.3+, then run stack setup && stack build to refresh dependencies.

• Clear Stack’s cached packages
  Stale cached packages can cause weird version mismatches that ignore your intended versions. Try running these commands to wipe the cache and start fresh:

  stack clean --full
  stack purge
  

  Then re-run stack build to pull down fresh copies of all dependencies, including the fixed Aeson version.

• Verify the actual Aeson version your project is using
  Run stack list-dependencies | grep aeson to see exactly which Aeson version your project is pulling in. If it’s still pre-1.6.1, a dependency in your tree is forcing an older version. Add an explicit constraint to your package.yaml (or .cabal file) to enforce the fixed version:

  dependencies:
    - aeson >= 1.6.3
  

  Then run stack build again to resolve the version conflict.

• Check the Yesod template’s dependency constraints
  Some Yesod templates have hardcoded dependency versions that override Stack’s settings. Open the template’s package.yaml or .cabal file to see if there’s an explicit Aeson constraint pinning it to an older version. If so, update that line to require Aeson 1.6.1+.

I’ve dealt with these kinds of version mismatch headaches plenty of times—these steps should help you get past the error and back to building your Yesod sites!

内容的提问来源于stack exchange，提问作者jaybee